Finally, after 30 months this conundrum is solved.
A friend of mine originally suggested Pseudospora and for a while I assumed it was indeed Pseudospora parasitica. Ferry, amongst others, suggested an amoeboid life form - Nuclearia delicatula. But N. delicatula is not known to produce cysts and I have seen and documented cysts. Other members of the Nuclearia group are not known to produce cysts.
In 1865 Cienkowsky first described Pseudospora and Nuclearia, both being parasites feeding on algae. Where Pseudospora has a flagellated and an amoeboid life form, Nuclearia has an amoeboid and a heliozoan life form. The literature on this parasites is sparse and many biologists in their books have copied information from others.
In 2011 it became evident that my unknown species was indeed not Pseudospora parasitica! When there is an abundance of Spirogyra, parasites are not far. While looking for fresh material from my unknown species I found Pseudospora parasitica. Indeed, I collected samples where both life forms were present. As it is clear now, only Pseudospora parasitica can drill holes in the cell wall. Nuclearia needs damaged cell walls (rotten). Being clever, Nuclearia opportunistically uses holes in cell walls drilled by P. parasitica to slip into Spiragyra cells! To make matters even more confusing, there is another parasite of the Cercozoa group found around those Spirogyra blooms - unknown to be a distinct species . The swarmer of this species is flagellated and confused me thoroughly. Research about this Cercozoa parasite is currently being published by a friend of mine. I will make this available to the forum after the paper is accepted.
This lead to confusing descriptions by the authors Cienkowsky, Zopf etc. and it did mislead me thoroughly, too.
In 2009, a new species of Nuclearia was isolated from a warm spring in Yunoko Lake, Japan. It has been given the name of Nuclearia thermophila. This year, a student for Biology working on his master thesis found an unknown nucleariid amoeba in the Zurich lake that has a 99% DNA match with the N. thermophila. It sometimes has more than one Nucleus and forms cysts. N. thermophila from nature has endosymbiotic bacteria that are believed to help Nuclearia to deal with the toxins of ingested Cyanobacteria! Comparing our observations showed that my strange nucleariid species was indeed N. thermophila!
Nuclearia is the basal form for all fungi. Pseudospora belongs to the Cercozoa group.
63x DIC, Nuclearia thermophila
amoeboid form inside Spirogyra
amoeboid form outside Spirogyra
amoeboid form outside Spirogyra
The ball shaped Nuclearia thermophila (heliozoic form) floats inactive in the water and is surrounded by bacteria. A couple of long filopodia can be recognized. N. thermophila produces two types of filopodia - long and short ones. The bacteria are endosymbiotic. Cultured Nuclearia thermophila loose these bacteria.
heliozoic form
After eating for nearly 24 hours P. parasitica develops hair-like filopodia and prepares for fission. Compare the forms of the two species to the left with the right one.
I never observed the fission. Once I found 2 species with more than one nucleus. Whether this is prior to fission of something else, I can not say (yet).
The next picture shows a well fed species in the heliozoic form (green) and an amoeboid form that is actively trying to get into the Spirogyra cell.
in the middle a cyst has been formed
cyst
cyst with two nuclei
I have made a small video: http://www.youtube.com/watch?v=SG05T14PFg8
My comments are in German but they are not so important anyway
I will post more pictures (also of Pseudospora parasitic) in the next couple of days to not exceed the posting limits of the forum.
Kind regards,
Ecki
